Effect of corticosterone on the hypothalamic-pituitary-gonadal system of male Japanese quail exposed to either short or long photoperiods

Influence of maternal corticosterone treatment on incubation length of eggs laid by Japanese quail hens selected for divergent adrenocortical stress responsiveness

1. Previous studies have shown that more yolk corticosterone is found in the eggs of random bred Japanese quail hens implanted with corticosterone during egg formation; both unstressed and stressed quail hens selected for exaggerated (high stress) rather than reduced (low stress) plasma corticosterone response to brief restraint deposit more corticosterone into their egg yolks. The length of egg incubation is also known to be shorter in eggs laid by high than low stress hens. 2. Here we investigated the interactive effects of quail stress line (low vs. high stress) with maternal corticosterone treatment (empty implant controls vs. corticosterone-implants) during egg formation on length of egg incubation. 3. Mean (+/-SEM) length of egg incubation for high stress control eggs (3973 +/- 04 h) was similarly shorter (by about 4.5 h) than that found for low stress control eggs (3928 +/- 02 h). In addition, on average, the incubation length of eggs laid by corticosterone-implanted hens (3929 +/- 05 h) was nearly 3 h shorter than that found for eggs laid by control hens (3958 +/- 02 h) regardless of stress line. 4. Line x hen-implant treatment effects on mean (+/-SEM) length of egg incubation partitioned in rank order as follows: low stress control (3978 +/- 05 h) > low stress corticosterone-implant (3959 +/- 07 h) > high stress control (3938 +/- 03 h) > high stress corticosterone-implant (3912 +/- 04 h). 5. Our original contention that selection for exaggerated adrenocortical responsiveness is associated with a reduction in the length of egg incubation was supported. Because maternal stress-induced elevations of yolk B are known to occur, the present findings of further shortenings of the hatching times of eggs of corticosterone-treated hens of both stress lines are also important to the poultry industry because they warn producers that unless stress in hens during egg formation is minimised, abbreviated egg incubation periods may result beyond the effects that a hen's genetic predisposition to adrenocortical stress responsiveness has on the length of egg incubation.

Ontogeny of the Cloacal Gland in Male Japanese Quail Classified in a T-Maze

Broiler chicks that traverse a T-maze quickly to reinstate contact with their companions (HP, high performers) are known to grow faster, are more social, and have a reduced plasma corticosterone response to acute stress than slower chicks (LP, low performers). High-performing quail from a line selected for reduced rather than exaggerated (high-stress) adrenocortical stress responsiveness also show enhanced female reproductive performance when compared with LP-high-stress quail. Herein, time courses of male sexual development were evaluated in genetically unremarkable quail that were categorized at 2 d of age as HP or LP in the T-maze. Body weight, cloacal gland volume (CVOL), proportion of individuals that produced cloacal gland foam, intensity of foam production, and CVOL relative to BW (RCVOL) were determined weekly from 4 to 10 wk of age, and again at 22 wk, along with absolute and BW-adjusted testes weight. Although CVOL and RCVOL were initially similar in both T-maze groups, both variables were greater (P < 0.05) in HP than in LP quail between 6 and 10 wk of age. High-performing birds also showed a trend (P < 0.1) of greater cloacal gland foam than their LP counterparts from 5 to 7 wk. From 8 wk on, all birds were in foam production. Intensity of foam production results generally mimicked those found for CVOL and RCVOL. Body weights were higher (P < 0.05) in HP than LP quail from 5 to 7 wk. No T-maze group differences were found in any of the variables at 22 wk of age. The results suggest that rapid negotiation of the T-maze is associated with accelerated growth and puberty in male quail, although the enhanced reproductive development of HP males does not remain extant in aged adults.

Maternal corticosterone further reduces the reproductive function of male offspring hatched from eggs laid by quail hens selected for exaggerated adrenocortical stress responsiveness

Activation of the hypothalamic-pituitary-adrenal (HPA) axis can depress the hypothalamic-pituitary-testicular axis. Male quail cloacal gland (CG) size and foam production shows androgen dependency, and males selected for exaggerated [high stress (HS)] rather than reduced [low stress (LS)] plasma corticosterone (B) stress response exhibit reduced CG and testes development. High stress hens also deposit more B into egg yolks than LS ones, and quail hens given B produce chicks that have a reduced growth rate and adults with heightened HPA responsiveness. Herein, we gave LS and HS hens no B [empty implants, control (CON)] or B-filled implants and assessed the reproductive performances of these hens and their male offspring. Mortality was similarly elevated in LS and HS B-treated hens, but only HS B-implanted hens showed reduced egg production. In male offspring, CG volume (CVOL), intensity of CG foam production (CFP), and the proportion of individuals that produced CG foam were measured from 4 to 11 wk of age. At 6 wk, BW, and at 15 wk, BW, testes weight (TWT), and TWT relative to BW were also determined. Hen treatments did not affect male chick CVOL at 4 wk, but CVOL differed thereafter as follows: LS CON > LS B = HS CON = HS B at 5 and 6 wk and LS CON > LS B > HS CON = HS B from 7 to 11 wk. By 8 wk, and thereafter, CFP differed as follows: LS CON > LS B > HS CON > HS B. Group differences in the proportion of individuals that produced CG foam generally supported CFP findings from 4 to 8 wk of age. Body weight did not differ by treatment at 6 wk of age. By 15 wk, TWT were similarly depressed in both HS groups. However, similarly higher 15-wk BW in the LS-CON and HS-B groups contributed to TWT relative to BW differences as follows: LS-B > LS-CON > HS-B; LS-CON = HS-CON; LS-B > HS-CON; and, HS-CON = HS-B. Both selection for exaggerated HPA responsiveness and maternal B treatment negatively affected the reproductive function of HS male offspring.

Cloacal Gland Growth Differences in High and Low Plasma Corticosterone Stress Response Line Male Quail Reared Under Short Daylengths

Mail quail selected (generation 32) for reduced [low stress (LS)] or exaggerated [high stress (HS)] plasma corticosterone stress response to brief mechanical restraint (5 min of immobilization) were studied for differences in the growth of their cloacal glands when reared essentially lifelong on short day lengths of 8L:16D. Post-brooding, at 4 wk of age, 96 quail (48 LS+48 HS) were housed in cages (1 LS and 1 HS male/cage), and the short day light treatment was instigated. Using a digital caliper, cloacal gland (CG) size measurements (length and width, mm) were made biweekly beginning at 42 d of age and ending at 196 d of age (28 wk old). The CG volume (CVOL) was calculated from these measurements using a literature-proposed formula. The CVOL in both lines increased similarly with increasing age from 6 to 12 wk of age. However, beginning at 14 wk of age and thereafter, LS males showed greater (P<0.05) CVOL than HS ones. No further increases in CVOL were observed in either line at 24 wk of age beyond that seen at 22 wk. This study demonstrated that although both lines show CG development under short days, eventually CG growth becomes comparatively stymied in the HS males. Furthermore, the maintenance of similarly lower CVOL in HS than LS males, CVOL that showed no further increase from 22 to 24 wk of age, suggests that holding these quail lifelong on short days results in, comparatively, yet another permanent negative reproductive consequence in quail selected for exaggerated plasma corticosterone stress responsiveness.

Cloacal Gland and Gonadal Photoresponsiveness in Male Japanese Quail Selected for Divergent Plasma Corticosterone Response to Brief Restraint

Corticosterone is linked to testicular depression, and in Coturnix, a relatively photorefractory species, day length and androgen dependency in cloacal gland development and foam production are evident. Furthermore, male quail selected for reduced (low stress, LS) rather than exaggerated (high stress, HS) plasma corticosterone stress response show more photo-induced reproductive development, greater resistance to reproductive declines induced by exposure to very short days, and a quicker recovery to a higher reproductive level upon return to long days. To determine whether a milder reduction in day length would also influence stress line reproductive photoresponsiveness, and perhaps photorefractoriness, males grown on 16 h of light were given 13 h of light for 4 wk followed by a return to long days for 12 wk. Cloacal gland measurements were made following the initial stimulatory photoperiod and weekly thereafter during the 2 light treatments. Plasma testosterone was determined initially, after 4 wk of light reduction, and at the end of the study, along with BW, testes weight (TWT), and TWT relative to BW. Cloacal gland volume (CVOL) was greater in LS than HS males grown on long days. Whereas exposure to 13 h of light reduced CVOL in both lines, line differences (LS > HS) persisted during the first 3 wk of light reduction. Moreover, by 2 wk of rephotostimulation, and weekly thereafter, line differences (LS > HS) in CVOL reemerged. Cloacal gland foam production and the proportion of individuals that produced cloacal gland foam responses reflected changes in CVOL. The BW did not differ by line, yet LS males had a higher TWT and TWT relative to BW than HS ones. All individuals, however, exhibited relative photorefractory responses. Whereas none of the LS males completely resisted reproductive regression induced by a 3 h light reduction, LS males showed other reproductive benefits upon mild photocastration and subsequent rephotostimulation (e.g., greater resistance to CVOL and cloacal gland foam production losses during a mild light crash and quicker restoration to full reproductive potential upon relighting).

Cloacal Gland and Testes Development in Male Japanese Quail Selected for Divergent Adrenocortical Responsiveness

The time course of sexual development in male quail from lines selected for either a reduced (low stress, LS) or an exaggerated (high stress, HS) plasma corticosterone response to brief restraint was determined. Sexual development was assessed by examination of cloacal gland area (CAREA) and volume (CVOL), proportion of individuals that produced cloacal gland foam, and the intensity of cloacal gland foam production (CFP) at 4, 5, 6, 8, 10, 14, and 16 wk of age. These intervals encompass ages during which growing, photostimulated quail would be expected to evolve from being totally prepubescent to well into adulthood. Testes weight (TW) and the proportion of individuals that had achieved a combined TW of 500 mg (PI500) were also measured at 6 and 16 wk of age. Mean CAREA and CVOL were similar in LS and HS quail at 4 wk of age. Beginning at 5 wk of age and thereafter, CAREA was greater (P < 0.05) in LS than in HS quail. Similarly, beginning at 6 wk of age and thereafter, CVOL was greater (P < 0.05) in LS than in HS quail. More LS than HS birds also expressed foam at 4 (P < 0.05), 5 (P = 0.15), and 6 wk (P < 0.05) of age. From 8 wk on, all birds were in foam production. CFP results mimicked those found for CAREA and CVOL in that LS quail tended toward higher CFP values than HS quail at all intervals of measurement. TW were higher (P < 0.02) in LS than HS quail when data from the 2 ages at which testes were harvested were combined. At 6 wk of age, the LS and HS birds showed a PI500 line difference (P < 0.08) of 1.0 and 0.91, respectively; by 16 wk, all birds exhibited a maximum PI500. The results suggest that 1) selection for reduced adrenocortical responsiveness in Coturnix is accompanied by an accelerated onset of puberty in males, and 2) enhanced reproductive development in LS males remains extant throughout early to middle-age adulthood.

Photoperiod-Induced Changes in Cloacal Gland Physiology and Testes Weight in Male Japanese Quail Selected for Divergent Adrenocortical Responsiveness

In quail, activation of the hypothalamic-pituitary-adrenal axis has been linked to depression in the hypothalamic-pituitary-testicular axis, and cloacal gland development and foam production are known to be androgen dependent. Therefore, photoperiod manipulations that induce gonadal growth (long day) and involution (short day) were used to examine changes in cloacal gland physiology in male quail from lines selected for a reduced (low stress, LS) or exaggerated (high stress, HS) plasma corticosterone response to brief restraint. Line differences in cloacal gland area (CAREA) and volume (CVOL), the proportion of individuals that produced cloacal gland foam (PICF), and the intensity of cloacal gland foam production (CFP) were initially assessed in adult males maintained on stimulatory, long photoperiods of 14L:10D. Thereafter, these variables were re-examined weekly in the same males during their subsequent exposure to 3 wk of short days (6L:18D) followed by return to long d for 3 more wk. Line differences in testes weight relative to body weight (RTW) were also measured at the end of the study. CAREA and CVOL were markedly greater in LS than HS males grown under long days. As expected, these indices of cloacal gland size were greatly reduced upon exposure to short days in both lines. However, line differences (LS > HS) in CAREA and CVOL were maintained during the first 2 wk of exposure to short days. Line differences in the depressed cloacal gland size measures were no longer evident by the third week on short days as well as after the first week of relighting wherein there were no further depressions in gland size of either line. However, by the end of 2 wk of rephotostimulation and thereafter, marked line differences (LS > HS) in CAREA and CVOL re-emerged. Photoperiod-induced line effects on CFP generally mimicked those of CAREA and CVOL. The PICF was marginally different (P < 0.07) between the lines (LS > HS) only after 1 wk of light reduction. After 3 wk of rephotostimulation, RTW was nearly 25% greater in LS quail. The results suggest that selection for reduced adrenocortical responsiveness in Coturnix has resulted in certain reproductive advantages in middle-aged, adult males maintained on stimulatory photoperiods as well as in such adults subjected to photocastration and subsequent rephotostimulation.

Selection of Japanese quail for reduced adrenocortical responsiveness accelerates puberty in males

Differences in the onset of puberty were assessed in male Japanese quail from a random-bred (RB, control) line and two lines that had been genetically selected for reduced (low stress, LS) or exaggerated (high stress, HS) plasma corticosterone response to brief mechanical restraint. At 42 d of age, cloacal gland area (CAREA) and volume (CVOL), proportion of individuals that produced cloacal gland foam (PICF), and intensity of cloacal gland foam production (CFP) were examined in 60 representatives from each of these quail lines. CFP was quantified by subjective scaling of the amount of foam ejected upon manual expression (squeezing) of the foam gland, using a scale of 1 (no foam expressed) to 5 (maximum amount of foam expression). Mean CAREA and CVOL were similar in quail of the RB and HS lines, but these measures were greater (P < 0.01) in the LS quail. In addition, more (P < 0.05) LS than HS birds expressed foam at 42 d, whereas RB quail exhibited an intermediate PICF response that was not different from either selected line. CFP results mimicked those found for PICF (i.e., LS quail produced a greater (P < 0.05) amount of foam than HS birds, whereas RB quail showed intermediate production that was not different from LS or HS levels). In prepubertal and pubertal Japanese quail, cloacal gland hypertrophy is androgen-dependent and highly positively correlated with testes size as well as sexual activity. Cloacal gland foam production is also considered a reliable indicator of testicular size and activity. Thus, we conclude that selection for reduced adrenocortical responsiveness in Coturnix is associated with acceleration in the onset of puberty in males. The potential interaction between adrenocortical and testicular activity as it relates to male reproductive performance is discussed.

Biochemical characterization and seasonal changes in the concentration of testosterone-metabolizing enzymes in the European great tit (Parus major) brain

Homogenates of diencephala obtained from brains of European great tits (Parus major) were incubated in the presence of tritiated testosterone (T) as precursor, and four metabolites produced from this steroid were formally identified and quantified. Conversion into 5 beta-dihydrotestosterone (5 beta-DHT) constituted the major metabolic pathway of T. Smaller amounts of 5 alpha-dihydrotestosterone (5 alpha-DHT), 5 beta-androstane-3 alpha, 17 beta-diol (5 beta-DIOL), and estradiol (E2) were also produced. The metabolism of T was time-dependent, and it varied as a function of the initial precursor concentration. The kinetics of 5 beta- and 5 alpha-reductases, as well as aromatase, followed the Michaelis-Menten model. It was found that 5 beta-reductase has a low apparent affinity for T, but is present in large concentrations. In contrast, the apparent affinity for T and the concentration of aromatase were approximately 3.9 times higher and 130 times smaller, respectively, than those of 5 beta-reductase. Intermediate values were found for 5 alpha-reductase. The validated assay was used to measure seasonal changes in the in vitro metabolism of T in the anterior (AH) and posterior (PH) hypothalamus and the cerebellum (CER) of free-living juvenile and adult male great tits. The production of 5 beta-DHT was low during the winter period in the PH of adult males, whereas the 5 beta-DIOL production was low in both parts of the hypothalamus at this time of the year. During autumn the production of these metabolites showed a transitory decrease in both parts of the hypothalamus of the juveniles. The production of 5 beta-reduced metabolites by the CER was high at all times of the year. In juveniles, the CER production of 5 beta-DHT did not change seasonally, whereas 5 beta-DIOL production peaked during summer. In the CER of adults, maximum production of both metabolites occurred during summer. Generally, less T was converted into 5 beta-reduced metabolites by the PH than by either the AH or the CER. E2 production was observed only in the AH and PH. With one exception (summer; AH), E2 production was high in both parts of the hypothalamus of adults throughout the year. In both AH and PH of juveniles, E2 production was low during summer. In these birds, it increased between summer and autumn in both parts of the hypothalamus, and also between autumn and winter in the PH. The production of 5 alpha-DHT did not change as a function of the season, the age of the birds, or the brain region.(ABSTRACT TRUNCATED AT 400 WORDS)

Testosterone metabolism and its testosterone-dependent activation in the uropygial gland of quail

The in vitro metabolism in the uropygial gland of the male quail results into large yields of 5 beta-reduced and/or 17 alpha-hydroxylated metabolites. This metabolism was studied in glands of sexually quiescent quails five days after a single intra-muscular injection of testosterone to the birds. This treatment led to an increased production of inactive metabolites (epitestosterone and its 5 beta-reduced metabolites) and to a decrease of unmetabolized testosterone. Thus testosterone controls its own metabolism and by this way means to modulate its action in the uropygial gland of quail.

Effect of progesterone on the sexual behavior of the male Japanese quail

The reduced metabolites of testosterone produced in the central nervous system of birds are known to be involved in the regulation of male sexual behavior. Since progesterone may compete with testosterone for 5 alpha- and 5 beta-reduction, it may also interfere with the sexual behavior of birds. In order to test this hypothesis, progesterone was administered to male quail either transferred from short days to long days or kept in short days and treated with testosterone. Sexual behavior and crowing were scored at intervals for 21 days and the size of the cloacal gland was measured at the same times. On Day 21, the birds were killed and their testes were weighed. The administration of a large dose (1 mg/day) of progesterone depressed the sexual behavior of the birds stimulated either by long days or by the administration of testosterone. It is suggested that progesterone may compete with testosterone for the active sites of 5 alpha- and 5 beta-reductase; alternatively, its effect may be due to an antiandrogenic activity.

Sexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males.